The present invention relates generally to containers, and, more particularly, to a container having a pressure relief apparatus and lid, and a method of manufacture of such a container.
Cooling containers are used to contain a variety of products and maintain such products at a reduced temperature relative to ambient temperature for a prolonged period of time. An example of a cooling container is disclosed in E. L. Smith U.S. Pat. No. 2,526,165, which describes (in connection with FIG. 6 therein) a container having an outer bowl that surrounds an inner bowl wherein the bowls are hermetically sealed to define a chamber therebetween. A suitable refrigerant liquid such as water is disposed within the chamber. A user places the container into a household freezer for a long enough period of time to freeze the refrigerant liquid. Thereafter, the user takes the container out of the freezer and may place a product, such as a perishable food item, within the container. The refrigerant liquid is capable of maintaining the food item placed in the container at a temperature below room temperature for a relatively long period of time.
Some prior art containers using a coolant or refrigerant within a cavity have included air space within the cavity to allow for expansion of the refrigerant upon freezing. Allowing for such expansion prevents such containers from rupturing. Another strategy to prevent such rupture of a cooling container is disclosed in Hilado U.S. Pat. No. 4,485,636 where the bottom of the cavity is formed by a resilient diaphragm. The diaphragm allows for expansion of the refrigerant by compressing in response to the expanding refrigerant, thereby increasing the volume of the cavity and preventing the walls of the container from breaking as a result of the expanding refrigerant.
While numerous prior art containers deal with pressure increases within a cavity due to expansion of refrigerant upon freezing, no known attempts have been made for handling pressure increases resulting from increased heat. It is possible that if a user were to place a prior art container having a substance in a sealed cavity within a microwave oven or near a radiant heat source, sufficient heat and pressure would develop within the sealed cavity to rupture the walls of the container.
In addition to the foregoing, it is desirable to have a lid that seals a container adequately over a broad temperature range. This can be difficult for containers and lids that expand or contract in response to temperature change. Some prior art containers and lids used therewith have dealt with expansion and contraction by constructing both the container and lid of a resilient material that accommodates such expansion or contraction. An example of such a container and lid is disclosed in Tupper U.S. Pat. No. 2,752,972. At least one type of container utilizes a lid wherein the lid and container have different coefficients of thermal expansion (xe2x80x9cCTExe2x80x9d). For example, Fishman U.S. Pat. No. 4,223,800 discloses a lid and a receptacle. The lid includes a top portion made of the same material as the receptacle and a bottom portion wherein the bottom portion is made of a resilient material with a greater CTE than the receptacle. The bottom portion is integral with a resilient bead. The resiliency of the bead causes the bead to deform into sealing engagement with a wall of the receptacle when the lid is placed on the receptacle. When the receptacle and lid are placed in a refrigerator the bottom portion shrinks to a greater degree than the receptacle. However, sealing engagement of the bead and the wall of the receptacle is maintained by the matching CTE""s of the top portion and the receptacle.
While numerous prior art containers incorporate lids that seal despite expansion of the container and/or lid, no known attempts have been made in the art to provide a lid that seals adequately despite expansion of a cooling container.
In accordance with one aspect of the present invention, a container comprises a sealed cavity defined by first and second walls of the container. A coolant is disposed within the cavity wherein the coolant is capable of assuming first and second phases. A portion of the first wall is joined to the second wall wherein the portion includes an off-center opening. The portion is rupturable to limit pressure in the sealed cavity. The container further comprises a container rim and a lid having an outer channel and a tab. The outer channel receives the container rim and defines a first width. The tab has a second width substantially equal to the first width. There is a first interference fit of the channel with the container rim when the coolant is in the first phase. There is a second interference fit, different than the first interference fit, when the coolant is in the second phase.
According to a further aspect of the invention, a method of manufacturing a container includes the steps of providing first and second container portions and placing a coolant in the second container portion. The first container portion is placed within the second container portion, a region of the second container portion is joined to the first container portion, and an opening is formed in the region.
A further alternative aspect of the present invention comprehends a method of manufacturing a container including the steps of providing a coolant within the container wherein the coolant is capable of assuming first and second phases and providing a lid that forms first and second seals with the container. A nominal interference for the first seal is selected and is effective when the container is exposed to a particular condition. The second seal ensures sealing of the lid with the container when the container is exposed to a condition other than the particular condition.
According to another aspect of the present invention, a container comprises a container body including a hollow cavity and a rim. A coolant is disposed within the hollow cavity wherein the coolant is capable of assuming first and second phases. A lid has a peripheral member wherein the peripheral member forms first and second seals with the rim and wherein the seals have different interference fits with the rim when the container is exposed to different temperatures.
According to a further aspect of the invention a lid for a container includes a peripheral member defining an outer channel. The peripheral member has a peripheral wall that carries a bead. The bead contacts a rim of the container. A tab extends from the peripheral wall and interrupts contact of the bead with the rim. The outer channel has a first width, and the tab has a second width substantially equal to the first width.
In accordance with a still further aspect of the invention, a lid for a container, includes an outer channel of a first width and a tab extending outwardly from the channel. The tab has a second width substantially equal to the first width.
In accordance with yet another aspect of the invention, a lid for a container comprises an outer channel defined by a peripheral wall that carries a bead. The bead contacts a rim of the container. A tab extends outwardly from the peripheral wall and interrupts contact of the bead with the rim.
Other aspects and advantages of the present invention will become apparent upon consideration of the following detailed description.